1. Field of the Invention
The present invention relates to a vibration proofing or suppressing system for suppressing the vibration of a civil or building structure under a disturbance such as an earthquake, wind or traffic vibration.
2. The Prior Art
A conventional system for suppressing the vibration of a structure through the utilization of a lever mechanism was disclosed in the Japanese Patent Laid-open No. 38340/75. Another conventional system of such a kind was developed by the present inventors through the improvement of the former system.
In the former conventional system, one end of an arm is provided with a weight as an auxiliary mass and the other end of the arm is pivotally coupled as a fulcrum to either a floorboard or the ceiling of a structure, while a wall with high rigidity is connected to the other floorboard. The intermediate point of the arm and the tip of the wall are coupled to each other by a link. The lever-ratio namely, the ratio of length from the fulcrum of the arm to the weight to the length from the fulcrum to the linkcoupled point of the arm, is made so large that a high counteracting force to suppress the vibration of the structure is generated by the movement of the weight although the weight is light.
In the latter conventional system, one end of a rocking arm is provided as a fulcrum to either a floorboard or the ceiling of a structure. The auxiliary mass is provided so that it can be moved in a horizontal straight direction along a straight movement guide unit. A structural member fixed to the other floorboard is connected through a link to a intermediate point of the rocking arm, and the auxiliary mass is also coupled through another link to the other end of the arm opposite to the fulcrum so that they are moved in conjunction with each other in which the ratio of the lengths of the two links is designed to be same as the lever-ratio of the rocking arm. This results in eliminating the drawbacks of the former conventional system, that is, if the length of lever is long, the reduction of the rigidity of the lever means causes higher modes of vibration, and if the length of the lever means is shortened to produce the high rigidity thereof, the auxiliary mass is moved along an arc by the swing of the lever means, whose behavior causes not only horizontal force required to suppress the vibration of the structure but also vertical force, which makes it difficult to suppress the vibration.
If a structure is multi-storied, systems can be obtained by modifying the latter conventional mechanism so as to be housed in the wall-like members which are provided in the stories of the structure to suppress the vibration thereof.
Furthermore, the present inventors developed the lever means system with the specified distribution of lever-ratios along the height of a multi-storied structure, the distribution of which are determined by making use of the function normalized by the participation factor of the selected mode of vibration, in which the masses, auxiliary masses and stiffnesses of springs are adjusted in order to make the selected eigen vector similar to the index vector of disturbance magnitude of an equation of motion for the whole structure, and thereby enhancing the vibration proofing and suppressing effect of the system.
If auxiliary masses are small for either a structure of ordinary height or a skyscraper, very large lever-ratios such as 50 and 80 are required even for the improved conventional system. However, it is very difficult to design members to meet the requirement. This is one disadvantage of the prior art systems.
Prior art technology is not known which provides a lever system with high damping capacity for structural members such as beams, pillars and piles or for an observatory, a bridge of large span or the like. This is another disadvantage of the prior art.